The transgenic core will have responsibility for helping laboratories work effectively with existing strains of transgenic mice, generate new strains of transgenic mice, and prepare chimeric animals for analyses of brain function. This core will maintain colonies of mice adequate for generating such animals, will generate and characterize lines of embryonic stem cells, help prepare mice with altered or mutated genes by homologous recombination, help prepare homozygous mutant embryonic stem cells for use in generating chimeric mice, and educate postdoctoral fellows and students in these techniques.